The present invention relates to polymeric foams. More specifically, the invention relates to foams of diphenylmethane diisocyanates which are useful as retrofit insulation.
In today's energy conservation conscious world, finding ways to better insulate our homes is foremost on the minds of a great many people. Many different materials have been used for such insulation. For example, fiberglass insulation provides good insulation characteristics for insulation of walls, ceiling, etc. of homes. However, a large number of homes have been built in the past without sufficient insulation in their walls. Obviously, it would be very costly to rip out the walls of a home to retrofit them with insulation materials such as fiberglass. Accordingly, methods which would avoid such destruction of the walls are extremely advantageous.
Various foam materials have been used in the past in an attempt to retrofit wall cavities with insulation materials. For example, ureaformaldehyde and phenol-formaldehyde foams have been previously used by pumping such foam into the wall cavity through a hole placed in the walls. Ureaformaldehyde foam, which is commercially more important, has a number of disadvantages including friability, release of toxic formaldehyde if poorly applied, shrinkage with subsequent loss of insulation effectiveness, and limited warm temperature resistance that prohibits its use in walls in warmer climates and in attics. The major drawback of loose-fill insulation products is settling with time, creating uninsulated voids in wall cavities. Impracticality prohibits the use of more conventional insulation materials (such as, urethane board stock, fiberglass, polystyrene, foamed glass, polyolefin foams) to retrofit wall sections simply because of the difficulty of manufacturing and/or installing at the site without extensive building damage.
Polyurethane and polyisocyanurate foams are well-known as effective insulation materials. However, using such prior polyurethane or polyisocyanurate foams to retrofit wall cavities with insulation has met with certain difficulties. First, the polyurethane or polyisocyanurate insulating foams have been too dense to make them economical as insulation for wall cavities. For example, most walls contain cavities in the range of three and five-eights inches thick. The amount of polyurethane or polyisocyanurate foam needed to fill these large cavities cannot be economically justified in terms of the insulation obtained by the foam, e.g., satisfactory insulation characteristics would be economically obtained with a foam about 2 inches thick. Moreover, the prior polyurethane or polyisocyanurate foams used to retrofit wall cavities with insulation have had other problems because they have rise times which exceed their gel or set times. Thus, such a foam first sets within the wall cavity to such an extent that the pressure generated within the cavity causes damage as the foam completes its expansion. Also, excess foam inadvertently admitted into the wall cavity will not continue to extrude through the access hole in the wall. The foam then continues to expand creating a pressure pushing on the walls of the cavity, in many instances causing buckling or even cracking of the walls.
Various disclosures of retrofitting wall cavities with foam materials are disclosed in the prior art. For example, U.S. Pat. No. 2,690,987 discloses a resin foamed structure in which an alkyd resindiisocyanate mixture is used as a coating composition on the inner face of the structure walls. A foaming composition containing diisocyanate is then introduced between the wall surfaces. The coating is said to aid the free rise of the foam during the gas evolution step and to lubricate the walls of the structure and allow a free rise of the foam.
A large number of other U.S. patents disclose certain polyurethane, polyisocyanurate and polycarbodiimide foams, e.g., Nos. 3,524,825; 3,666,848; 3,876,567; 3,884,917; 3,887,501; 3,896,052; 3,965,052; 3,984,359; 4,092,276; 4,101,465 and 4,129,097. A number of these patents disclose, i.a., foams containing methylene chloride and/or water, but none of these patents disclose the production of a rigid, closed cell foam suitable for retrofitting wall cavities with insulating material by employing a softening agent and water to provide a foam having a low density, good insulation characteristics, and a rise time greater than gel or set time. Moreover, it is the general teaching in the art that the inclusion of materials such as methylene chloride in foams should be avoided especially in rigid foams because such materials tend to dissolve the polymers causing degradation and discoloration of the polymers. In addition, others have reported that these materials cause the polymers to shrink, warp badly, and turn brown, see for example Frost's U.S. Pat. Nos. 3,391,093 and 3,072,582.